###### tags: `HPCAI`

[TOC]
# High Performance Communications
## Networt Metrics
### Terminology
#### Channel properties (between two points)
- Latency(delay)延遲：一個封包從來源端送出後，到目的端接收到這個封包，中間所花的時間

- Round trip time(RTT)：封包往返時間

- Bandwidth(BW)頻寬
- the rate of passing messages
- volume per time ,or frequency (byte per second)

>BW is the width of a road (cars/sec)
>Latency is the length (in hours to drive)

- Loss/drop rate
- the rate at which a message is sent but not received
- 傳出去但沒收到
- Jitter
- At the sending side, packets are sent in a continuous stream with the packets spaced evenly apart.
- Jitter is when there is a time delay in the sending of these data packets over your network connection.
- [Reference](https://www.cisco.com/c/en/us/support/docs/voice/voice-quality/18902-jitter-packet-voice.html)

#### Topological properties
- Network topology網路拓撲
- shape of network connection (weighted graph of entities)
- 指構成網路的成員間特定的排列方式
> Network is a city
> The topology is the road map

[Reference](https://www.dnsstuff.com/what-is-network-topology)


- [Bisection Bandwidth](https://www.youtube.com/watch?v=SsRcAJfa7J4)
- the minimal bandwidth between two halves of the network

- Routing protocol dynamics
- The way messages are routed across the network
- ***Dynamic routing*** is a process where a router forward data via a different routeor given destination within system

|路由|動態|靜態|
| :------: | ------ | ----------- |
|手動輸入|不需要|需要|
|缺點|速度慢|如果網路拓撲改變，須更新資料到路由器設備中|
|優點|一旦網路架構有任何的改變，不須要做太多事情來管理|速度快、不須經過學習|
|適合|有變動的網路拓撲|不會有變動的網路拓撲|

:::info
**Router路由器**
決定封包從來源端到目的端所經過的路徑(host 到host之間的傳輸路徑)
A packet is typically forwarded from one router to another router through the networks
:::

#### Application properties
- [Traffic composition](https://cloud.google.com/apigee/docs/api-platform/analytics/traffic-composition-dashboard?hl=nb-no#trafficcomposition)

- Traffic pattern

### Motivation: Hardware improvements

### Throughout
- The rate of successful message delivery over a communication channel
- Throughput depends on the packet size, jitter and other network properties

### Point-to-point (p2p) measurements
#### ping

#### iperf

-s : 啟動 Server 模式，如iperf3 -s
-c : 啟動 Client 模式，如iperf3 -c xxx.xxx.xxx.xxx(或機器名稱)
-t : 監視測量時間，如-t 90設定監測是為90秒
-w : 測試傳輪檔案大小，如 -w20M
-i : 指定輸出數據的間隔時間，如-i 3
-p : iPerf3預設會使用的5201連接埠，例如-p 12345來更改

#### [My home Wifi](https://beta.speedtest.net/)